This is an example of XSS-Track ability to dump WebSockets communication. This blog post explains more.
This is a modified vulnerable version of socket.io chat application
I've set up a test WebSocket server to go with it here but it won't last long, so to test it yourself follow these steps:
$ cd blog-kotowicz-net-examples/track-xss/vuln/socket.io/example
$ node server.js